The invention relates to a process for the recovery of solubilized polysaccharides, in particular nonionic glucans from solution. Further, the invention relates to the recovery of polysaccharides by using a divalent cation and a water miscible organic solvent to precipitate the polysaccharides from solution.
Current procedures teach the use of an alcohol such as isopropyl alcohol or acetone for the recovery of nonionic polysaccharides, in particular glucan from fermentation media and other solutions containing the glucan. Generally, the clarified media is concentrated to a flowable viscosity and then precipitated with 50% by volume solvent. The precipitate is drained and then successively treated with higher concentrations of the water miscible organic solvent. This process which requires concentration to reduce media volumes and large quantities of solvent is an expensive, capital intensive procedure.
U.S. Pat. No. 3,759,896 discloses a process to produce polysaccharides with antitumor activity mainly consisting of B-(1.fwdarw.3)-linked D-glucose residue by obtaining culture filtrates of fungi belonging to Ascomycetes, Basidiomycetes and Fungi imperfecti and then purifying the culture filtrate by sequential treatments of acidification, deionization by ion exchange resins and precipitation with a water soluble miscible solvent.
U.S. Pat. No. 4,072,567 discloses a process for producing a water-insoluble glucan by cultivating a Streptococcus microrganism in a liquid medium and recovering the glucan by sedimentation, filtration or seiving. The crude glucan is further processed by dissolving in sodium hydroxide, centrifuging, neutralizing with hydrogen chloride and then washing.
Glucan derivatives have also been produced by reacting water-insoluble B-1,3 glucan with a cyanogen halide to produce water-insoluble carriers, see U.S. Pat. No. 4,075,405.
Xanthomonas gum, an anionic polysaccharide is a fermentation product of the bacteria Xanthomonas campestris. The gum is recovered from the fermentation broth by precipitation. Known precipitating agents for the gum are calcium ion combined with an alkaline pH, isopropyl alcohol and a quaternary compound, see U.S. Pat. No. 4,053,699.
It is desirable to find novel methods to recover solubilized polysaccharides from solution. Further, it is desirable to reduce recovery costs of the polysaccharide as an economic improvement for commercializing a process to produce and recover polysaccharides.
Polysaccharides have been used extensively in the chemical, oil, pharmaceutical, food, cosmetic and paper manufacturing industries. The process of the instant invention is useful in that nonionic polysaccharides, in particular glucans are useful as viscosifiers, binders, thickeners and stabilizers in industrial and food applications. Glucans have various industrial applications such as enhanced oil recovery and oil well drilling muds, tablet coatings, opthalmic solutions, antiacid suspensions, porcelain and ceramic glazes, ceramic binders, water-based paints, paper coatings, printing inks, integrated circuit chips, agricultural seed coatings, pesticide sprays and the like.
It is an object of the instant invention to recover nonionic polysaccharides, in particular glucans from solution. It is another object of the instant invention to recover polysaccharides from solution by the addition of a divalent cation in concert with a water miscible organic solvent.
These and other objects, together with the advantages over known methods shall become apparent from the specification which follows and are accomplished by the invention as herein described and claimed.